In the field of angiography and angioplasty, it is common for a relatively thick guidewire (e.g. 0.035 inch) to be initially inserted through the cardiovascular system of a patient to the area of a stenosis in a coronary artery. Following this, a guiding catheter may be advanced along the guidewire to a position in the arterial system, typically the aortic root, following which the guidewire may be withdrawn, and replaced with a thinner guidewire (e.g. 0.010-0.018 in.), which is then advanced across the stenosis.
After this has been accomplished, an angioplasty catheter, for example, may be advanced through the guiding catheter and along the thin guidewire which traverses the stenosis, with the hope and expectation that the angioplasty catheter also can pass through the stenosis, to bring a balloon into position for the angioplasty procedure (PTCA).
All things being equal, the cardiologist typically prefers a smaller guiding catheter French size, which requires a smaller access site and PTCA introducer sheath, which carries with it less risk of hematoma. However, the particular interventional situation may turn out to require a larger guiding catheter, after the cardiologist has emplaced the narrower PTCA guidewire, for example so that a stent, a Rotoblader unit, a perfusion balloon, or other technology may be inserted. This may have to be done on an emergency basis, requiring immediate withdrawal of the guiding catheter and introducer and replacement with a larger guiding catheter and introducer.
It has been found, in this circumstance, that it may not be possible to withdraw the guiding catheter for any reason without pulling the thin distal tip of the guidewire with it, even if the proximal guidewire end is being manually held. Thus, the position of the guidewire traversing the stenosis may be lost, and this loss may be permanent and irretrievable in unfavorable situations. Thus, it may not be possible to replace a guidewire that has crossed a stenosis.
Additionally, a stiffer guiding catheter or different curve style may be needed to facilitate passage of the guidewire and or balloon through the stenosis and intricate portions of the arterial system. Here also, a replacement of the guiding catheter may be required, and as before, the PTCA guidewire may be dragged back with the withdrawing guiding catheter, so that the cardiologist loses a position of guidewire advancement that he worked so hard to achieve.
Castaneda et al. U.S. Pat. No. 5,417,669 discloses an exchange catheter used to help prevent guidewire withdrawal during guiding catheter exchange.
In accordance with this invention, a catheter exchange method is provided in which the advancement position of even a very thin and flexible guidewire may be preserved, while a catheter surrounding the guidewire is exchanged, such as a guiding catheter, or the guidewire itself may be exchanged, with the new guidewire returning to the same advancement position.
There is a body of prior art pertaining to "rapid exchange" catheters, which typically have an aperture in their sides such as a hole or a slit, thus permitting exchange of the balloon without the use of a guidewire extension attached to the proximal end of the guidewire. However, these prior art catheters and techniques fail to solve all of the problems addressed by this invention. Particularly, with respect to a very thin or very flexible guidewire, the above are not used effectively to inhibit the withdrawal of the distal end of the guidewire along with a withdrawing guiding catheter, even if the proximal end of the guidewire is being held in place.